This invention relates to a method which comprises treating the load-bearing surface of the endless belt of a conveyor system with a release agent which is operative to cause bituminous sands subsequently deposited on the belt to separate cleanly therefrom when the belt rounds the end roller of the system.
The invention finds application with respect to a conveyor belt of nitrile or other rubber composition used to convey bituminous sands from a storage bin to a hot water process extraction circuit for recovering bitumen from the sands.
Bituminous sands, when dropped onto a conveyor belt from a height of several feet, tend to adhere to the belt surface when it rounds the end roller. Some of the adhering sands remain attached to the belt and build up on it to form an uneven load thereon. Other portions of the sands drop off the belt as it returns to the starting point of the system. To give some idea of the magnitude of this latter problem, in the 125,000 barrels of bitumen produced per day facility being constructed by the assignees of this invention, it is estimated that, in the absence of a suitable release agent, a deposit of tar sand 17 feet high would be generated beneath the conveyor belt each day. Indeed, provision has been made to permit mechanical shovels to drive beneath the conveyor belt to remove this material.
Out of doors, the problem has been solved by applying a liquid hydrocarbon, such as diesel fuel, to the belt surface before the sands are deposited thereon. However, this prior art belt release agent cannot be used on the conveyor belt connecting the storage bin and the conditioning drum in a hot water process extraction plant, as the belt is housed and the danger of fire or an explosion is too great.
In seeking a release agent for use on this belt, a set of criteria which the agent must satisfy has been developed. More particularly, the release agent must:
(A) WHEN APPLIED TO THE BELT IN MODERATE VOLUME, EFFECTIVELY CAUSE THE SANDS TO RELEASE FROM THE BELT SURFACE WHEN IT IS UNLOADING AT THE END ROLLER;
(B) BE NON-FLAMMABLE;
(C) NOT BE HARMFUL TO THE HOT WATER EXTRACTION PROCESS;
(D) NOT BE HARMFUL TO THE CONVEYOR BELT MATERIAL NOR RENDER REPAIR DIFFICULT SHOULD DAMAGE OCCUR TO THE BELT; AND
(E) BE NON-TOXIC AND NON-CORROSIVE.